X THE STARRY HEAVENS 415 



sixteen years, is at most one two-thousand- 

 milliontli part as bright. Nevertlieless, as 

 long ago as 1815 Fraunhofer recognised the 

 fixed lines in the light of four of the Stars ; 

 in 1863 Miller and Huggins in our own 

 country, and Rutherford in America, suc- 

 ceeded in determining the dark lines in the 

 spectrum of some of the brighter Stars, thus 

 showing that these beautiful and mysterious 

 lights contain many of the material substances 

 with which we are familiar. In Aldebaran, 

 for instance, we may infer the presence of 

 hydrogen, sodium, magnesium, iron, calcium, 

 tellurium, antimony, bismuth, and mercury. 

 As might have been expected, the composition 

 of the Stars is not uniform, and it would 

 appear that they may be arranged in a few 

 well-marked classes, indicating differences of 

 temperature, or perhaps of age. 



Thus we can make the Stars teach us their 

 own composition with light, which started 

 from its source years ago, in many cases long 

 before we were born. 



Spectrum analysis has also thrown an un- 

 expected light on the movements of the Stars. 



